Abstract
Leaf-cutting ants (Atta spp. and Acromyrmex spp.; Attini, Formicidae) are highly polymorphic, and cut and carry leaf tissue fragments that vary widely in size. A positive correlation between worker size and fragment size typically occurs (Rudolph and Loudon 1986; Lighton et al., 1987; Roces, 1990; Wetterer, 1990, 1991a, 1994; Shutler and Mullie, 1991; Roces and Ndfiez, 1993; Roces and Hrlldobler, 1994), but it is uncertain whether ants can shift the correlation according to differing foraging circumstances, so that ants of a fixed size cut and carry fragments of greater or smaller area. The issue of variability in load matching also arises because of theoretical arguments concerning advantages to social foragers from appropriate facultative adjustment of the load size-ant size relation during leaf harvesting (Roces and Nfifiez, 1993; Kacelnik, 1993). Lutz (1929) and Weber (1972) suggested that load selection in attines is a passive consequence of worker body size and the cutting technique of the ants. Workers anchor themselves to the margin of a leaf with their metathoracic legs and cut arcs through the leaf with a radius that depends inflexibly on their body length, according to this "reach hypothesis." Evidence reflecting on the reach hypothesis has been contradictory. No effect of distance from the nest on load size-ant size matching for Atta cephalotes in Cost Rica was found in an exper-
Published Version
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